As shown in Japanese Patent Application Laid-Open No. 348487/1999, a writing instrument in which a liquid ink and an ink occlusion body (sliver) having an outer skin are mounted in an ink tank has so far been known. The writing instrument having such structure does not deteriorate so much the writing performances of a free ink type writing instrument which have so far been exhibited, and has the effect of preventing an ink from leaking to the outside of the writing instrument even when air in the inside of the ink tank is expanded due to a change in temperature and pressure. However, the writing instrument shown in Japanese Patent Application Laid-Open No. 348487/1999 has the following problem that arises from mounting therein an ink occlusion body (sliver) having an outer skin, though having the effect of preventing an ink from leaking.
Conventional problems shall be explained with reference to FIG. 9 and FIG. 10. A method for charging an ink occlusion body (sliver) and an ink into an ink tank includes various methods. It includes, for example, a method in which an ink is charged into an ink tank to some extent and then an ink occlusion body impregnated with the ink is charged into the ink tank, a method in which an ink is charged into an ink tank and then an ink occlusion body impregnated with no ink is charged into the ink tank and a method in which, as shown in FIG. 9, an ink occlusion body 3 is charged into an ink tank 1 and then the ink occlusion body 3 is impregnated with an ink 6 while introducing the ink into the ink tank 1. In these methods, the ink occlusion body 3 has to be impregnated with the ink 6 from a lower part thereof so that air does not remain in the inside of the ink occlusion body 3.
A prescribed amount of the ink is charged thereinto, and then an ink holder 7 is pressed into the ink tank 1 from its aperture to complete a writing instrument. After completion, the writing instrument is upset to turn a pen tip part 9 downward, so that the ink 6 passes through between an outer skin 2 and the inner wall of the ink tank 1 to flow toward the pen tip part 9. No problem is brought about when the ink occlusion body 3 is completely impregnated with the ink, but if not completely impregnated, the ink occlusion body starts to be impregnated with the ink as well from the lower part (pen tip part 9 side) thereof, so that a void part 13 is produced in the ink occlusion body 3. If writing is continued in this state, caused are the problems that the void part 13 makes it impossible to effectively consume the ink in the upper part (reverse side to the pen tip part 9) than the void part 13 and that the void part causes inferior writing. These problems are liable to be brought about even if any of the charging methods described above is employed.
Further, when an ink occlusion body is merely mounted in an ink tank, the state that a gas-liquid exchange part is not wetted is brought about in a certain case, and an ink head applied to a pen tip is increased. As a result, the problem that an ink leaks from a pen tip part is caused.
An object of the present invention is to solve the problems brought about when an ink occlusion body having an outer skin is mounted in the inside of an ink tank, that is, to provide a writing instrument which prevents an ink void part from being produced in the ink occlusion body and which can effectively consume an ink and does not cause inferior writing.
Further, an object thereof is to solve the problem that when an ink occlusion body is mounted in an ink tank, an ink head applied to a pen tip is increased and as a result, an ink leaks from a pen tip part.